<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
function handleDragStart(e) {
  this.style.opacity = '0.4';  // this / e.target is the source node.
}

var cols = document.querySelectorAll('#columns .column');
[].forEach.call(cols, function(col) {
  col.addEventListener('dragstart', handleDragStart, false);
});
</script>
</head>
<body>
<div id="columns">
  <div class="column" draggable="true"><header>A</header></div>
  <div class="column" draggable="true"><header>B</header></div>
  <div class="column" draggable="true"><header>C</header></div>
</div>

</body>
</html>